Background: Psychosocial factors are argued to increase cancer risk. This study aims to clarify the association between various psychosocial factors and cancer incidence (including breast, lung, prostate, and colorectal cancers) via individual-participant data (IPD) meta-analysis. The psychosocial factors considered were perceived social support (PSS), loss, relationship status, neuroticism, and general distress.
Methods: The Psychosocial Factors and Cancer Incidence consortium used data from 22 cohorts with a measure of at least one psychosocial variable of interest at baseline (up to N = 421,799; cancer incidence, N = 35,319; person-years of follow-up, N = 4,378,582). In stage 1 of the IPD meta-analysis, Cox regression models were used with age as the timescale. In stage 2, results were pooled in random-effects meta-analyses.
Results: No psychosocial factors were associated with an increased risk of overall cancer and with breast, prostate, and colorectal cancers, as well as with cancers with alcohol as a common potential causal factor. PSS, currently not in a relationship, and a loss event were associated with an increased risk of lung cancer (hazard ratio [HR], 1.09-1.55). Estimates decreased for PSS and relationship status when adjusting for several known risk factors, such as a family history of cancer (HR, 1.05-1.08). Similar findings were observed for relationship status and cancers with tobacco smoking as a common potential causal factor.
Conclusions: For most types of cancer, psychosocial factors (measured at a single point in time) were not associated with increased risk. PSS, currently not in a relationship, and loss were associated with an increased risk of lung cancer, although most effects attenuated when adjusting for several known risk factors.
Keywords: cancer incidence; loss; neuroticism; prospective; relationship; social support; stress.